Memory cell containing copolymer containing diarylacetylene portion

ABSTRACT

An organic memory cell containing an organic semiconductor layer containing a copolymer is disclosed. The copolymer contains a diarylacetylene portion and at least one of an arylacetylene portion and a heterocyclic acetylene portion. The copolymer may be a random copolymer, an alternating copolymer, a random block copolymer, or a block copolymer. Methods of making an organic memory devices/cells containing the copolymer, methods of using the organic memory devices/cells, and devices such as computers containing the organic memory devices/cells are also disclosed.

FIELD OF INVENTION

The subject invention relates generally to organic memory cells and, inparticular, to organic memory cells containing a copolymer containing adiarylacetylene portion and at least one of an arylacetylene portion andheterocyclic acetylene portion.

BACKGROUND OF THE INVENTION

The basic functions of a computer and memory devices include informationprocessing and storage. In typical computer systems, these arithmetic,logic, and memory operations are performed by devices capable ofreversibly switching between two states often referred to as “0” and“1.” Such switching devices are fabricated from semiconducting devicesthat perform these various functions and are capable of switchingbetween two states at high speed.

Electronic addressing or logic devices, for instance for storage orprocessing of data, are made with inorganic solid-state technology, andparticularly crystalline silicon devices. The metal oxide semiconductorfield effect transistor (MOSFET) is one the main workhorses.

Much of the progress in making computers and memory devices faster,smaller and cheaper involves integration, squeezing ever moretransistors and other electronic structures onto a postage stamp sizedpiece of silicon. A postage stamp-sized piece of silicon may containtens of millions of transistors, each transistor as small as a fewhundred nanometers. However, silicon-based devices are approaching theirfundamental physical size limits.

Inorganic solid-state devices are generally encumbered with a complexarchitecture that leads to high cost and a loss of data storage density.The circuitry of volatile semiconductor memories based on inorganicsemiconductor material must constantly be supplied with electric currentwith a resulting heating and high electric power consumption in order tomaintain stored information. For example, nonvolatile semiconductordevices have a reduced data rate and relatively high power consumptionand large degree of complexity.

SUMMARY OF THE INVENTION

The following is a summary of the invention in order to provide a basicunderstanding of some aspects of the invention. This summary is notintended to identify key/critical elements of the invention or todelineate the scope of the invention. Its sole purpose is to presentsome concepts of the invention in a simplified form as a prelude to themore detailed description that is presented later.

The subject invention provides an organic memory cell containing acopolymer in an organic semiconductor layer, the copolymer containing adiarylacetylene portion and at least one of an arylacetylene portion andheterocyclic acetylene portion. The subject invention also provides anorganic memory cell containing a copolymer containing adiphenylacetylene portion and a phenylacetylene portion. The organicmemory cell possesses one or more of the following: small size comparedto inorganic memory cells/devices, capability to store multiple bits ofinformation, short resistance/impedance switch time, low operatingvoltages, low cost, high reliability, long life (thousands/millions ofcycles), capable of three dimensional packing, associated lowtemperature processing, light weight, high density/integration, andextended memory retention.

One aspect of the subject invention relates to a method of making anorganic memory cell containing a copolymer in an organic semiconductorlayer, the copolymer containing a diarylacetylene portion and at leastone of an arylacetylene portion and heterocyclic acetylene portion. Thesubject invention also relates to a method of making an organic memorycell containing a copolymer containing a diphenylacetylene portion and aphenylacetylene portion. The organic semiconductor layer may be formedby a chemical vapor deposition (CVD) process. The copolymer may beformed by polymerization of diarylacetylene in the presence of at leastone of arylacetylene and heterocyclic acetylene.

To the accomplishment of the foregoing and related ends, the inventioncomprises the features hereinafter fully described and particularlypointed out in the claims. The following description and the annexeddrawings set forth in detail certain illustrative aspects andimplementations of the invention. These are indicative, however, of buta few of the various ways in which the principles of the invention maybe employed. Other objects, advantages and novel features of theinvention will become apparent from the following detailed descriptionof the invention when considered in conjunction with the drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates a perspective view of a three dimensionalmicroelectronic device containing a plurality of organic memory cells inaccordance with one aspect of the invention.

FIG. 2 illustrates a perspective view of a three dimensionalmicroelectronic device containing a plurality of organic memory cells inaccordance with another aspect of the invention.

FIG. 3 shows a cross sectional view of forming an organic memory cell inaccordance with one aspect of the invention.

FIG. 4 shows a cross sectional view of forming an organic memory cell inaccordance with one aspect of the invention.

FIG. 5 shows a cross sectional view of forming an organic memory cell inaccordance with one aspect of the invention.

FIG. 6 shows a cross sectional view of forming an organic memory cell inaccordance with one aspect of the invention.

FIG. 7 shows a cross sectional view of forming an organic memory cell inaccordance with one aspect of the invention.

FIG. 8 shows a cross sectional view of forming an organic memory cell inaccordance with one aspect of the invention.

FIG. 9 shows a cross sectional view of forming an organic memory cell inaccordance with one aspect of the invention.

FIG. 10 shows a cross sectional view of forming an organic memory cellin accordance with one aspect of the invention.

FIG. 11 shows a cross sectional view of forming an organic memory cellin accordance with one aspect of the invention.

DISCLOSURE OF THE INVENTION

The subject invention includes an organic memory cell containing acopolymer in an organic semiconductor layer, the copolymer containing adiarylacetylene portion and at least one of an arylacetylene portion andheterocyclic acetylene portion. The subject invention also includes anorganic memory cell containing a copolymer in an organic semiconductorlayer, the copolymer containing a diphenylacetylene portion and aphenylacetylene portion. The copolymer may be a random copolymer, analternating copolymer, a random block copolymer, or a block copolymercontaining the diarylacetylene portion and at least one of thearylacetylene portion and heterocyclic acetylene portion.

The subject invention involves a method of making an organic memory cellcontaining a copolymer in an organic semiconductor layer, the copolymercontaining a diarylacetylene portion and at least one of anarylacetylene portion and heterocyclic acetylene portion. The subjectinvention also more specifically involves a method of making an organicmemory cell containing a copolymer in an organic semiconductor layer,the copolymer containing a diphenylacetylene portion and aphenylacetylene portion. The copolymer exhibits improved thermalstability and improved density compared to polymers made with only onemonomer. Since semiconductor processing in general involves numerousacts requiring high temperatures, the improved thermal stability of thecopolymer based organic semiconductor layers of the subject invention isa significant advance.

The organic memory cells contain at least two electrodes, as one or moreelectrodes may be disposed between the two electrodes that sandwich thecontrollably conductive media. The electrodes are made of conductivematerial, such as conductive metal, conductive metal alloys, conductivemetal oxides, conductive polymer films, semiconductive materials, andthe like. The controllably conductive media contains an organicsemiconductive layer and passive layer.

The organic memory cells may optionally contain additional layers, suchas additional electrodes, charge retention layers, and/or chemicallyactive layers between or in addition to the two electrodes and thecontrollably conductive media. The impedance of the controllablyconductive media changes when an external stimulus such as an appliedelectric field is imposed. A plurality of organic memory cells, whichmay be referred to as an array, forms an organic memory device.

An organic semiconductor layer can be formed over a passive layer. Theorganic semiconductor layer comprises a copolymer that contains adiarylacetylene portion and at least one of an arylacetylene portion andheterocyclic acetylene portion. The formation of the organicsemiconductor layer can be carried out by any suitable process, forexample a chemical vapor deposition (CVD) process. The copolymer may bea random copolymer, an alternating copolymer, a random block copolymer,or a block copolymer containing the diarylacetylene portion and at leastone of the arylacetylene portion and heterocyclic acetylene portion.

Referring to FIG. 1, a brief description of a microelectronic organicmemory device 100 containing a plurality of organic memory cells 104 inaccordance with one aspect of the invention is shown, as well as anexploded view 102 of an exemplary organic memory cell 104. Themicroelectronic organic memory device 100 contains a desired number oforganic memory cells, as determined by the number of rows, columns, andlayers (three dimensional orientation described later) present. Thefirst electrodes 106 and the second electrodes 108 are shown insubstantially perpendicular orientation, although other orientations arepossible to achieve the structure of the exploded view 102. Each organicmemory cell 104 contains a first electrode 106 and a second electrode108 with a controllably conductive media 110 therebetween. Thecontrollably conductive media 110 contains an organic semiconductorlayer 112 and a passive layer 114. Peripheral circuitry and devices arenot shown for brevity.

The organic memory cells 104 contain at least two electrodes, as one ormore electrodes may be disposed between the two electrodes that sandwichthe controllably conductive media 110. The electrodes are made ofconductive material, such as conductive metal, conductive metal alloys,conductive metal oxides, conductive polymer films, semiconductivematerials, and the like.

Examples of electrodes include one or more of aluminum, barium, calcium,chromium, cobalt, copper, germanium, gold, magnesium, manganese,molybdenum, indium, iron, nickel, palladium, platinum, silver, titanium,tungsten, zinc, and alloys thereof, indium-tin oxide (ITO) and indiumzinc oxide and other conductive metal oxides; polysilicon; dopedamorphous silicon; metal silicides, metal carbides, and metal nitrides;and the like. Alloy electrodes specifically include Hastelloy®, Kovar®,Invar, Monel®, Inconel®, brass, stainless steel, magnesium-silver alloy,and various other alloys.

When a copper sulfide passive layer 114 is formed on the surface of anelectrode by contacting a sulfur compound with the electrode, theelectrode that is adjacent the copper sulfide layer contains at leastcopper, so as to permit formation of a copper sulfide layer by thesulfur treatment. In one embodiment, the electrode that is adjacent thecopper sulfide layer contains at least 50% by weight copper.

The electrode 106, 108 has a suitable thickness that depends upon thechosen implementations and/or the memory device being fabricated. In oneembodiment, the thickness of each electrode is independently about 0.01μm or more and about 10 μm or less. In another embodiment, the thicknessof each electrode is independently about 0.05 μm or more and about 5 μmor less. In yet another embodiment, the thickness of each electrode isindependently about 0.1 μm or more and about 1 μm or less.

The controllably conductive media 110, disposed between the twoelectrodes, can be rendered conductive or non-conductive in acontrollable manner using an external stimulus. Generally, in theabsence of an external stimulus, the controllably conductive media isnon-conductive or has high impedance. Further, in some embodiments,multiple degrees of conductivity/resistivity may be established for thecontrollably conductive media 110 in a controllable manner. For example,the multiple degrees of conductivity/resistivity for the controllablyconductive media 110 may include a non-conductive state, a highlyconductive state, and a semiconductive state.

The controllably conductive media 110 can be rendered conductive,non-conductive or any state therebetween (degree of conductivity) in acontrollable manner by an external stimulus (e.g., originating fromoutside the controllably conductive media). For example, under anexternal electric field, radiation, and the like, a given non-conductivecontrollably conductive media is converted to a conductive controllablyconductive media.

The controllably conductive media 110 contains one or more organicsemiconductor layers 112 and one or more passive layers. In oneembodiment, the controllably conductive media 110 contains at least oneorganic semiconductor layer 112 that is adjacent a passive layer(without any intermediary layers between the organic semiconductor layerand passive layer).

The organic semiconductor layer 112 comprises a copolymer containing adiarylacetylene portion and at least one of an arylacetylene portion andheterocyclic acetylene portion. The diarylacetylene portion and thearylacetylene portion may independently contain at least one ofmonocyclic aromatic hydrocarbon group containing from about 6 to about18 carbon atoms and fused polycyclic aromatic hydrocarbon group. In oneembodiment, the diarylacetylene portion and the arylacetylene portionmay independently contain a phenyl group; the diarylacetylene portionmay be made from diphenylacetylene and the arylacetylene portion may bemade from phenylacetylene. In another embodiment, the diarylacetyleneportion and the arylacetylene portion may independently contain fusedpolycyclic aromatic hydrocarbon group. The diarylacetylene portion andthe arylacetylene portion may be respectively made from diarylacetyleneand arylacetylene containing the fused polycyclic aromatic hydrocarbongroup. Examples of the fused polycyclic aromatic hydrocarbon group mayinclude naphthyl group, anthryl group, phenanthryl group, naphthacenylgroup, pyrenyl group, triphenylenyl group, and chrysenyl group. Examplesof diarylacetylene containing the fused polycyclic aromatic hydrocarbongroup may include phenylnaphthylacetylene, dinaphtylacetylene, andphenylphenanthrylacetylene. Examples of arylacetylene containing thefused polycyclic aromatic hydrocarbon group may includenaphthylacetylene, phenanthrylacetylene, and pyrenylacetylene.

The copolymer may include a heterocyclic acetylene portion. Examples ofthe heterocyclic acetylene portion may include pyridyl, pyridazinyl,pyrimidyl, pyrazinyl, quinolyl, isoquinolyl, quinazolinyl, cinnolinyl,and phthalazinyl group. For example, the heterocyclic acetylene portionmay be made from ethynylpyridine, ethynylpyridine, ethynylpyrimidine,ethynylquinoline, or ethynylquinazoline.

At least one of the diarylacetylene portion, the arylacetylene portion,and heterocyclic acetylene portion may have at least one substitutedgroup thereon. For example, the substituted diarylacetylene portion maybe made from (t-butyl)diphenylacetylene,(trifluoromethyl)diphenylacetylene, (trimethylsilyl) diphenylacetylene,(carbazole)diphenylacetylene, nitrodiphenylacetylene,methoxydiphenylacetylene, and related substituted diphenylacetylenes anddinaphthylacetylenes. The substituted arylacetylene portion may be madefrom, for example, p-methylphenylacetylene, p-dodecylphenylacetylene,o-amylphenylacetylene, methylphenylacetylene, methylnaphthylacetylene,hexylnaphthylacetylene, methoxyphenylacetylene, methylphenylacetylene,(t-butyl)phenylacetylene, nitro-phenylacetylene,(trifluoromethyl)phenylacetylene, (trimethylsilyl)phenylacetylene, andp-carbazolephenylacetylene. The substituted heterocyclic acetyleneportion may be made from, for example, 2-amino-5-ethynylpyridine,2-methyl-5-ethynylpyridine, 4-methyl-5-ethynylpyridine, and the like.

The copolymer can be formed by any suitable technique. For example, thecopolymer is formed by a chemical vapor deposition (CVD) process. In oneembodiment, the copolymer is formed by random polymerization ofdiarylacetylene in the presence of at least one of arylacetylene andheterocyclic acetylene. The resultant copolymer is a random copolymercontaining the diarylacetylene portion and at least one of thearylacetylene portion and heterocyclic acetylene portion. For example,the copolymer is formed by polymerization of diphenylacetylene in thepresence of phenylacetylene. In another embodiment, the copolymer isformed by block polymerization of diarylacetylene and at least one ofarylacetylene and heterocyclic acetylene. A thin layer containing atleast one of arylacetylene portion and heterocyclic acetylene portion isfirst formed, and then a diarylacetylene is introduced to a reactor anda thin layer of polydiarylacetylene is formed on the thin layercontaining at least one of the arylacetylene portion and heterocyclicacetylene portion. The resultant copolymer is a block copolymercontaining diarylacetylene portion and at least one of arylacetyleneportion and heterocyclic acetylene portion. In yet another embodiment,the copolymer may be an alternating copolymer or a random blockcopolymer containing the diarylacetylene portion and at least thearylacetylene portion and heterocyclic acetylene portion.

The copolymer has a suitable weight ratio of diarylacetylene portion toportion of arylacetylene and heterocyclic acetylene that depends uponthe chosen implementations and/or the memory device being fabricated. Inone embodiment, the copolymer contains from about 0.05% to about 99.95%by weight of the diphenylacetylene portion and from about 99.95% toabout 0.05% by weight of the arylacetylene and/or the heterocyclicacetylene portion. In another embodiment, the copolymer contains fromabout 50% to about 99.9% by weight of the diphenylacetylene portion andfrom about 50% to about 0.1% by weight of the arylacetylene and/or theheterocyclic acetylene portion.

Organic semiconductors thus have a carbon-based structure, often acarbon-hydrogen based structure, which is different from conventionalMOSFETs. The organic semiconductor materials are typically characterizedin that they have overlapping π orbitals, and/or in that they have atleast two stable oxidation states. The organic semiconductor materialsare also characterized in that they may assume two or more resonantstructures. The overlapping π orbitals contribute to the controllablyconductive properties of the controllably conductive media 110. Theamount of charge injected into the organic semiconductor layer 112 alsoinfluences the degree of conductivity of the organic semiconductor layer112.

The copolymer may contain other conjugated organic portions that weremade from a monomer having an acetylene bond in addition to thediarylacetylene portion and at least one of arylacetylene portion andheterocyclic acetylene portion. The conjugated organic polymer may belinear or branched, so long as the polymer retains its conjugatednature. Conjugated polymers are characterized in that they haveoverlapping π orbitals. Conjugated polymers are also characterized inthat they may assume two or more resonant structures. The conjugatednature of the conjugated organic polymer contributes to the controllablyconductive properties of the controllably conductive media 110.

The organic semiconductor layer 112 has the ability to donate and acceptcharges (holes and/or electrons). Generally, the organic semiconductoror an atom/moiety in the polymer has at least two relatively stableoxidation states. The two relatively stable oxidation states permit theorganic semiconductor to donate and accept charges and electricallyinteract with the conductivity-facilitating compound. The ability of theorganic semiconductor layer 112 to donate and accept charges andelectrically interact with the passive layer also depends on theidentity of the conductivity-facilitating compound.

In one embodiment, the organic semiconductor layer 112 is not doped witha salt. In another embodiment, the organic semiconductor layer 112 isdoped with a salt. A salt is an ionic compound having an anion andcation. General examples of salts that can be employed to dope theorganic semiconductor layer 112 include alkaline earth metal halogens,sulfates, persulfates, nitrates, phosphates, and the like; alkali metalhalogens, sulfates, persulfates, nitrates, phosphates, and the like;transition metal halogens, sulfates, persulfates, nitrates, phosphates,and the like; ammonium halogens, sulfates, persulfates, nitrates,phosphates, and the like; quaternary alkyl ammonium halogens, sulfates,persulfates, nitrates, phosphates, and the like.

The organic semiconductor layer 112 has a suitable thickness thatdepends upon the chosen implementations and/or the memory device beingfabricated. In one embodiment, the organic semiconductor layer 112 has athickness of about 0.001 μm or more and about 5 μm or less. In anotherembodiment, the organic semiconductor layer 112 has a thickness of about0.001 μm or more and about 2.5 μm or less. In yet another embodiment,the organic semiconductor layer 112 has a thickness of about 0.05 μm ormore and about 1 μm or less.

The organic semiconductor layer 112 may be formed by chemical vapordeposition (CVD) optionally including a gas reaction or gas phasedeposition. During formation or deposition, the organic semiconductormaterial self assembles between the electrodes. It is not typicallynecessary to functionalize one or more ends of the organic polymer inorder to attach it to an electrode/passive layer 114. It is to beappreciated that any suitable organic semiconductor layer formationprocesses may be employed with the subject invention. Choice of asuitable organic semiconductor layer formation process depends primarilyon the identity of the organic semiconductor layer material, size ofsubstrates being processed, and to some extent, the composition of apassive layer or dielectric layer. It is important to understand thateach of the various organic semiconductor layer formation processes hasits own set of features and characteristics well known in the art.

Any suitable CVD including a gas-phase reaction with the copper sulfidepassive layer 114 may be employed with the subject invention. The CVDgenerally contains a muffle component and a gas delivery component to achamber. The muffle generates gaseous chemicals containingdiarylacetylene, arylacetylene, and/or heterocyclic acetylene. The gasdelivery component introduces the gaseous chemicals to the chamber anddeposits an organic semiconductor layer 112 on the passive layer 114. Inone embodiment, the muffle provides a mixture of gaseous chemicals ofdiphenylacetylene and phenylacetylene to the chamber and forms randomcopolymer containing a diphenylacetylene portion and a phenylacetyleneportion on the copper sulfide passive layer 114. In yet anotherembodiment, the muffle first provides gaseous chemicals containingphenylacetylene to the chamber and forms a thin layer ofpolyphenylacetylene on the copper sulfide passive layer 114, and thenthe muffle provides gaseous chemicals containing diphenylacetylene tothe chamber and forms a thin layer of polydiphenylacetylene on thepolyphenylacetylene layer. The resultant copolymer is a block copolymercontaining a diphenylacetylene portion and a phenylacetylene portion.

A covalent bond may be formed between the organic semiconductor material112 and the passive layer 114. Alternatively, close contact is requiredto provide good charge carrier/electron exchange between the organicsemiconductor layer 112 and the passive layer 114. The organicsemiconductor layer 112 and the passive layer 114 are electricallycoupled in that charge carrier/electron exchange occurs between the twolayers.

The passive layer 114 can contain at least one conductivity-facilitatingcompound that contributes to the controllably conductive properties ofthe controllably conductive media 110. The conductivity-facilitatingcompound has the ability to donate and accept charge carriers (ions,holes and/or electrons). The passive layer 114 thus may transportbetween an electrode and the organic polymer layer/passive layerinterface, facilitate charge-carrier injection into the organic polymerlayer, and/or increase the concentration of charge carriers in theorganic polymer layer. In some instances, the passive layer 114 maystore opposite charges thereby providing a balance of charges in theorganic memory device as a whole. Storing charges/charge carriers isfacilitated by the existence of two relatively stable oxidation statesfor the conductivity-facilitating compound.

Generally, the conductivity facilitating compound or an atom in theconductivity-facilitating compound has at least two relatively stableoxidation states. The two relatively stable oxidation states permit theconductivity-facilitating compound to donate and accept charges andelectrically interact with the organic semiconductor layer 112. Theparticular conductivity facilitating compound employed in a givenorganic memory cell is selected so that the two relatively stableoxidation states match with the two relatively stable oxidation statesof the organic semiconductor material. Matching the energy bands of tworelatively stable oxidation states of the organic semiconductor materialand the conductivity facilitating compound facilitate charge carrierretention in the organic semiconductor layer 112.

Matching energy bands means that the Fermi level of the passive layer isclose to the valence band of the organic semiconductor layer 112.Consequently, the injected charge carrier (into the organicsemiconductor layer) may recombine with the charge at the passive layerif the energy band of the charged organic semiconductor layer 112 doesnot substantially change. Matching energy bands involves compromisingbetween ease of charge injection and length of charge (data) retentiontime.

The applied external field can reduce the energy barrier between passivelayer 114 and organic layer 112 depending on the field direction.Therefore, enhanced charge injection in the forward direction field inprogramming operation and also enhanced charge recombination in reversedfield in erase operation can be obtained.

The passive layer 114 contains at least copper sulfide. It is noted thatthe term copper sulfide layer or region in an organic memory cell 104refers to a portion of a memory element or memory cell that containsCu_(x)S_(y), as a conductivity-facilitating compound. In one embodiment,x and y are independently from about 0.5 to about 4. In anotherembodiment, x and y are independently from about 0.75 to about 3. Commonexamples of Cu_(x)S_(y) compounds include Cu₂S₃, CuS, Cu_(1.5)S, Cu₂S,Cu_(2.5)S, Cu₃S, and the like. For simplicity and brevity, all suchcopper sulfide layers falling within the noted Cu_(x)S_(y) formula aregenerically referred to as copper sulfide layers. Theconductivity-facilitating compound does not dissociate into ions underthe strength of the electric field. The passive layer 114 may containtwo or more sub-passive layers, each sub-layer containing the same,different, or multiple conductivity facilitating compounds.

The copper sulfide passive layer 114 may in some instances act as acatalyst when forming the organic semiconductor layer 112. In oneembodiment, the copper sulfide passive layer 114 may facilitatecopolymerizing diarylacetylene and at least one of arylacetylene andheterocyclic acetylene. In another embodiment, the copper sulfidepassive layer 114 may facilitate forming a polymer containing at leastone of an arylacetylene portion and a heterocyclic acetylene portion andthen growing polydiarylacetylene. In this connection, the polymerbackbone of the conjugated organic polymer may initially form adjacentthe passive layer 114, and grow or assemble away in a substantiallyperpendicular manner relative to the passive layer surface. As a result,the polymer backbones of the conjugated organic polymers areself-aligned in a direction that traverses the two electrodes.

The passive layer 114 may be on/between electrodes grown using oxidationtechniques, formed by chemical vapor deposition (CVD) optionallyincluding a gas reaction or gas phase deposition, formed by physicalvapor deposition (PVD) including vacuum evaporation, implantationtechniques, and sputter deposition, and the like. It is to beappreciated that any suitable passive layer formation processes may beemployed with the subject invention. Choice of a suitable passive layerformation process depends primarily on the identity of the passive layermaterial, size of substrates being processed, and to some extent, thecomposition of an electrode layer or dielectric layer. It is importantto understand that each of the various passive layer formation processeshas its own set of features and characteristics well known in the art.

In one embodiment, a passive layer 114 may be formed using CVDtechniques. Any suitable passive layer formation components using CVDtechniques may be employed with the subject invention. For example, anatmospheric pressure CVD (APCVD), low-pressure CVD (LPCVD),plasma-enhanced CVD (PECVD), high density CVD (HDCVD), or high densityplasma (HDP) may be employed.

In one embodiment, a passive layer 114 may be formed by a PECVD. ThePECVD typically contains a plasma generating component and a gasdelivery component. The PECVD can form various types of passive layer114 that includes one or more of the following: copper sulfide (Cu₂S,CuS) copper oxide (CuO, Cu₂O), manganese oxide (MnO₂), titanium dioxide(TiO₂), indium oxide (I₃O₄), silver sulfide (Ag₂S, AgS), iron oxide(Fe₃O₄), and the like. In accordance with one or more aspects of thesubject invention, the PECVD may form a thin film of conductivityfacilitating material such as copper sulfide (Cu₂S, CuS) on a conductivelayer to act as a passive layer 114 and facilitate conductivity betweenthe conductive layer and other layers that will subsequently be formedto contain a stack making up a memory cell. The PECVD introduces agaseous form of copper sulfide above a first electrode 106, with heliumoptionally being utilized as a carrier gas, through the gas deliverycomponent. The PECVD may optionally utilize a metal organic gasprecursor in the process which facilitates depositing the conductivityfacilitating compound at a relative low pressure and temperatureconditions (e.g., about 0.2 Pa. and from about 200° C. to about 300° C.,respectively). The metal organic precursor can be, for example, chelateCu (II) diethyldithiocarbamate or Cu(S₂CN(C₂H₅)₂)₂ (II).

In one embodiment, the passive layer 114 may be formed using oxidationtechniques. For example, a passive layer 114 containing copper sulfideis formed by contacting a sulfide compound with a first electrode 106containing copper in the following manner. When a copper sulfide layeris employed as a passive layer 114, the copper sulfide layer is formedover a substrate or in memory structure by initially and optionallyremoving or reducing copper oxide that be present on the structurecontaining at least copper. The copper oxide structure may be a copperelectrode or a copper pad within an electrode, the electrode with acopper pad or copper electrode adjacent to the subsequently formedcopper sulfide passive layer 114. Copper oxide tends to be very porous,and thus by removing or reducing copper oxide if present, uniformity inthe thickness of the subsequently formed copper sulfide layer and theadhesion between the copper sulfide layer and the organic semiconductorlayer 112 is improved. Moreover, removing copper oxide facilitates theformation of a copper sulfide layer with the exposed or upper regions ofthe structure containing at least copper.

Copper oxide removal or reduction, if performed, is carried out in anysuitable manner. In one embodiment, the copper oxide on the structuresurface may be removed by contacting a reducing agent such as NH₃ withthe structure. In another embodiment, the structure containing thecopper oxide on the structure surface may be heated at sufficienttemperature and for a sufficient period of time to facilitate oxideremoval/reduction. When heating the structure containing the copperoxide, the atmosphere contains one or more inert gases, with or withoutammonia, and preferably consists essentially of one or more inert gases.In this connection, in one embodiment, when heating the structurecontaining the copper oxide, the atmosphere contains essentially anitrogen gas.

After optional copper oxide removal/reduction, a sulfide compound iscontacted with the structure containing at least copper to form a coppersulfide layer in a portion of the structure. The copper sulfide may beformed over the entire surface of the structure containing at leastcopper, or a mask such as a patterned photoresist may cover portions ofthe surface of the structure, thus limiting copper sulfide formation tothe portions of the structure exposed through the openings in the mask.

The sulfide compound is capable of reacting with copper to form a coppersulfide layer within or on the original structure containing at leastcopper. Sulfide compounds include Group IA element and other suitablesulfides. Examples of sulfide compounds include hydrogen sulfide,lithium sulfide, sodium sulfide, potassium sulfide, ammonium sulfide,and the like.

The sulfide compound is contacted with the structure containing at leastcopper in the form of a sulfide compound mixture. In one embodiment, thesulfide compound mixture contains from about 0.1% to about 100% byweight of at least one sulfide compound and from about 0% to about 99.9%by weight of at least one inert gas. For example, the sulfide compoundmixture may contain about 2% by weight of at least one sulfide compoundand about 98% by weight of at least one inert gas.

The sulfide compound is contacted with the structure containing at leastcopper for a time at a temperature and at a pressure sufficient tofacilitate formation of a layer of copper sulfide in a portion of thestructure. In one embodiment, the sulfide compound is contacted with thestructure containing at least copper for a time from about 1 second toabout 60 minutes at a temperature from about 15° C. to about 500° C. andat a pressure from about 0.0001 Torr to about 1,000 Torr.

The passive layer 114 has a suitable thickness that depends upon thechosen implementations and/or the memory device being fabricated. In oneembodiment, the passive layer 114 containing the conductivityfacilitating compound has a thickness of about 2 Å or more and about 0.1μm or less. In another embodiment, the passive layer 114 has a thicknessof about 10 Å or more and about 0.01 μm or less. In yet anotherembodiment, the passive layer 114 has a thickness of about 50 Å or moreand about 0.05 μm or less.

In order to facilitate operation of the organic memory cells 104, theorganic semiconductor layer 112 is thicker than the passive layer 114.In one embodiment, the thickness of the organic semiconductor layer 112is from about 10 to about 500 times greater than the thickness of thepassive layer 114. In another embodiment, the thickness of the organicsemiconductor layer 112 is from about 20 to about 100 times greater thanthe thickness of the passive layer 114.

The area size of the individual organic memory cells 104 (as measured bythe surface area of the two electrodes directly overlapping each other)can be small compared to conventional silicon based inorganic memorycells such as metal oxide semiconductor field effect transistors(MOSFETs). In one embodiment, the area size of the organic memory cells104 of the subject invention is about 0.0001 μm² or more and about 4 μm²or less. In another embodiment, the area size of the organic memorycells 104 is about 0.001 μm² or more and about 1 μm² or less.

Operation of the organic memory devices/cells is facilitated using anexternal stimuli to achieve a switching effect. The external stimuliinclude an external electric field and/or light radiation. Under variousconditions, the organic memory cell 104 is either conductive (lowimpedance or “on” state) or non-conductive (high impedance or “off”state).

The organic memory cell 104 may further have more than one conductive orlow impedance state, such as a very highly conductive state (very lowimpedance state), a highly conductive state (low impedance state), aconductive state (medium level impedance state), and a non-conductivestate (high impedance state) thereby enabling the storage of multiplebits of information in a single organic memory cell 104, such as 2 ormore bits of information or 4 or more bits of information.

Switching the organic memory cell 104 to the “on” state from the “off”state occurs when an external stimuli such as an applied electric fieldexceeds a threshold value V_(on). Switching the organic memory cell 104to the “off” state from the “on” state occurs when an absolute value ofexternal stimuli exceeds an absolute value of another threshold V_(off).The threshold values vary depending upon a number of factors includingthe identity of the materials that constitute the organic memory cell104 and the passive layer 114, the thickness of the various layers, andthe like.

Generally speaking, the presence of an external stimuli such as anapplied electric field that exceeds a threshold value V_(on) permits anapplied voltage to write and that is less than threshold value V_(off)to erase information into/from the organic memory cell 104 and thepresence of an external stimuli such as an applied electric field thatis less than V_(on) but more than V_(off) permits an applied voltage toread information from the organic memory cell 104.

To write information into the organic memory cell 104, a voltage orpulse signal that exceeds the threshold is applied. To read informationwritten into the organic memory cell 104, a voltage or electric field ofany polarity is applied. Measuring the impedance determines whether theorganic memory cell 104 is in a low impedance state or a high impedancestate (and thus whether it is “on” or “off”). To erase informationwritten into the organic memory cell 104, a negative voltage or apolarity opposite the polarity of the writing signal that exceeds athreshold value is applied.

The organic memory devices described herein can be employed to formlogic devices such as central processing units (CPUs); volatile memorydevices such as DRAM devices, SRAM devices, and the like; input/outputdevices (I/O chips); and non-volatile memory devices such as EEPROMs,EPROMs, PROMs, and the like. The organic memory devices may befabricated in planar orientation (two dimensional) or three-dimensionalorientation containing at least two planar arrays of the organic memorycells 104.

In the subject invention, an organic semiconductor layer 112 contains acopolymer, the copolymer containing a diarylacetylene portion and atleast one of an arylacetylene portion and heterocyclic acetyleneportion. The organic semiconductor layer 112 has an enhanced thermalstability because of a high thermal stability of the diarylacetyleneportion in the organic semiconductor layer 112. Therefore, the organicsemiconductor layer allows organic memory cells to withstand hightemperatures of subsequent processes such as metal layer deposition,thus improving productivity and quality of organic memory devices.

Referring to FIG. 2, a three-dimensional microelectronic organic memorydevice 200 containing a plurality of organic memory cells in accordancewith an aspect of the invention is shown. The three-dimensionalmicroelectronic organic memory device 200 contains a plurality of firstelectrodes 202, a plurality of second electrodes 204, and a plurality ofmemory cell layers 206. Between the respective first and secondelectrodes are the controllably conductive media (not shown). Theplurality of first electrodes 202 and the plurality of second electrodes204 are shown in substantially perpendicular orientation, although otherorientations are possible. The three-dimensional microelectronic organicmemory device is capable of containing an extremely high number ofmemory cells thereby improving device density. Peripheral circuitry anddevices are not shown for brevity.

The impedance of the controllably conductive media changes when anexternal stimulus such as an applied electric field is imposed. Aplurality of organic memory cells, which may be referred to as an array,forms an organic memory device. In this connection, organic memory cellsmay form an organic memory devices and function in a manner analogous toMOSFETs in conventional semiconductor memory devices.

Referring to FIGS. 3 to 7 and FIGS. 8 to 11, two of many possibleexemplary embodiments of forming a memory cell in accordance with thesubject invention are illustrated. Specifically referring to FIG. 3, anelectrode 300 containing at least copper is provided in this example.The electrode 300 may be a layer of copper or a copper alloy layer.

Referring to FIG. 4, a copper oxide layer 302 may form over theelectrode 300 containing at least copper. Often times, the thickness ofthe copper oxide layer 302 is a function of time when the electrode 300containing copper is exposed to the ambient atmosphere. That is, oxygennormally present in air can oxidize the surface of a copper or copperalloy metal.

Referring to FIG. 5, the structure is heated to a temperature of about400° C. for 15 seconds in a gas atmosphere containing essentially of NH₃to remove the copper oxide layer 302 from the electrode 300 containingcopper. After the copper oxide layer 302 is removed, within the samechamber, a sulfide compound mixture containing about 10% by weight ofhydrogen sulfide and about 90% by weight of nitrogen is contacted withthe electrode 300 for a time from about 25 minutes at a temperatureabout 50° C. to form a copper sulfide region 304 within the electrode300. The copper oxide reduction/removal is optional in the sense thatthe copper sulfide region may be formed in the electrode 300 containingcopper before copper oxide forms on the electrode 300 surface.

Referring to FIG. 6, an organic semiconductor layer 306 containing acopolymer containing a diphenylacetylene portion and at least one of anarylacetylene portion and heterocyclic acetylene portion is formed overthe copper sulfide region 304 using CVD techniques. The copolymercontains from about 0.05% to about 99.95% by weight of diarylacetyleneportion and from about 99.95% to about 0.05% by weight of thearylacetylene portion and heterocyclic acetylene portion. For example,an organic semiconductor layer 306 containing a random copolymercontaining about 95% by weight of diphenylacetylene portion and 5% byweight of phenylacetylene portion is formed over the copper sulfideregion 304 using CVD techniques. The organic semiconductor layer 306 hasa thickness of about 1000 Å in this example.

Referring to FIG. 7, another electrode 308 is formed over the organicsemiconductor layer 306 to provide organic memory cell 310. In thisexample, the electrode 308 contains aluminum.

Referring to FIG. 8, a structure 400 containing a first electrode 402 isprovided. In this example, the first electrode 402 is a substratecontaining at least copper. The structure 400 may be a layer of adielectric.

Referring to FIG. 9, a copper oxide layer 404 may form over the firstelectrode 402. Often times, the thickness of the copper oxide layer 404is a function of time when the first electrode 402 is exposed to theambient atmosphere. That is, oxygen normally present in air can oxidizethe surface of a copper or copper alloy metal.

Referring to FIG. 10, the structure is heated to a temperature of about410° C. for 15 seconds in a gas atmosphere containing essentially NH₃ toremove the copper oxide layer 404 from the first electrode 402. Afterthe copper oxide layer 404 is removed, a sulfide compound mixturecontaining about 2% by weight of hydrogen sulfide and about 98% byweight of nitrogen is contacted with the first electrode 402 for about25 minutes at a temperature of about 75° C. to form the copper sulfideregion 408.

Referring to FIG. 11, an organic semiconductor layer 410 containing acopolymer containing a diphenylacetylene portion and at least one of anarylacetylene portion and heterocyclic acetylene portion is formed overthe copper sulfide region 408 using CVD techniques. The copolymercontains from about 0.05% to about 99.95% by weight of thediarylacetylene portion and from about 99.95% to about 0.05% by weightof the arylacetylene portion and heterocyclic acetylene portion. Forexample, the organic semiconductor layer 410 is a two-layer blockcopolymer that is made by first forming a thin polyphenylacetylene layerover the copper sulfide region 408 using CVD techniques and then byforming polydiphenylacetylene layer on the polyphenylacetylene layer.The block copolymer contains about 95% by weight of diphenylacetyleneportion and 5% by weight of phenylacetylene portion. The organicsemiconductor layer 410 has a thickness of about 1000 Å in this example.

A second electrode 412 is formed over the organic semiconductor layer410. In this example, the electrode 412 contains aluminum. A dielectricencasement layer 414 is formed thereover. Consequently, organic memorycell 416 is provided.

The organic memory cells/devices are useful in any device requiringmemory. For example, the organic memory devices are useful in computers,appliances, industrial equipment, hand-held devices, telecommunicationsequipment, medical equipment, research and development equipment,transportation vehicles, radar/satellite devices, and the like.Hand-held devices, and particularly hand-held electronic devices,achieve improvements in portability due to the small size andlightweight of the organic memory devices. Examples of hand-held devicesinclude cell phones and other two way communication devices, personaldata assistants, palm pilots, pagers, notebook computers, remotecontrols, recorders (video and audio), radios, small televisions and webviewers, cameras, and the like.

Although the invention has been shown and described with respect to acertain preferred embodiment or embodiments, it is obvious thatequivalent alterations and modifications will occur to others skilled inthe art upon the reading and understanding of this specification and theannexed drawings. In particular regard to the various functionsperformed by the above described components (assemblies, devices,circuits, etc.), the terms (including any reference to a “means”) usedto describe such components are intended to correspond, unless otherwiseindicated, to any component which performs the specified function of thedescribed component (i.e., that is functionally equivalent), even thoughnot structurally equivalent to the disclosed structure which performsthe function in the herein illustrated exemplary embodiments of theinvention. In addition, while a particular feature of the invention mayhave been disclosed with respect to only one of several embodiments,such feature may be combined with one or more other features of theother embodiments as may be desired and advantageous for any given orparticular application.

1. A method of making an organic memory cell comprising: providing afirst electrode; providing a passive layer comprising at least coppersulfide over the first electrode; forming an organic semiconductor layerover the passive layer, the organic semiconductor layer comprising acopolymer comprising a diarylacetylene portion and at least one of anarylacetylene portion and a heterocyclic acetylene portion; and forminga second electrode over the organic semiconductor layer.
 2. The methodof claim 1, wherein the first electrode comprises at least copper. 3.The method of claim 1, wherein the copolymer is a random copolymer, analternating copolymer, a random block copolymer, or a block copolymer.4. The method of claim 1, wherein the diarylacetylene portion and thearylacetylene portion independently comprises at least one of amonocyclic aromatic hydrocarbon group comprising from about 6 to about18 carbon atoms and a fused polycyclic aromatic hydrocarbon group. 5.The method of claim 4, wherein the monocyclic aromatic hydrocarbon groupis a phenyl group.
 6. The method of claim 4, wherein the fusedpolycyclic aromatic hydrocarbon group is at least one selected from thegroup consisting of a naphthyl group, an anthryl group, a phenanthrylgroup, a naphthacenyl group, a pyrenyl group, a triphenylenyl group, anda chrysenyl group.
 7. The method of claim 1, wherein the heterocyclicacetylene portion comprises at least one selected from the groupconsisting of a pyridyl group, a pyridazinyl group, a pyrimidyl group, apyrazinyl group, a quinolyl group, an isoquinolyl group, a quinazolinylgroup, a cinnolinyl group, and a phthalazinyl group.
 8. The method ofclaim 1, wherein at least one of the diarylacetylene portion, thearylacetylene portion, and the heterocyclic acetylene portion has atleast one substituted group thereon.
 9. The method of claim 1, whereinthe copolymer comprises a diphenylacetylene portion and aphenylacetylene portion.
 10. The method of claim 1, wherein thecopolymer comprises from about 50% to about 99.9% by weight of thediarylacetylene portion and from about 50% to about 0.1% by weight of atleast one of the arylacetylene portion and the heterocyclic acetyleneportion.
 11. The method of claim 1, wherein the organic semiconductorlayer has a thickness of about 0.001 μm or more and about 5 μm or lessand the passive layer has a thickness of about 2 Å or more and about 0.1μm or less.
 12. A method of making an organic memory cell comprising:providing a first electrode; providing a passive layer comprising atleast copper sulfide over the first electrode; forming an organicsemiconductor layer over the passive layer, the organic semiconductorlayer comprising a copolymer, the copolymer comprising from about 0.05%to about 99.95% by weight of the diarylacetylene portion and from about99.95% to about 0.05% by weight of at least one of the arylacetyleneportion and the heterocyclic acetylene portion; and forming a secondelectrode over the organic semiconductor layer.
 13. The method of claim12, wherein the first electrode comprises at least copper.
 14. Themethod of claim 12, wherein the copolymer is a random copolymer, analternating copolymer, a random block copolymer, or a block copolymer.15. The method of claim 12, wherein the diarylacetylene portion and thearylacetylene portion independently comprises at least one of amonocyclic aromatic hydrocarbon group comprising from about 6 to about18 carbon atoms and a fused polycyclic aromatic hydrocarbon group. 16.The method of claim 15, wherein the monocyclic aromatic hydrocarbongroup is a phenyl group.
 17. The method of claim 15, wherein the fusedpolycyclic aromatic hydrocarbon group is at least one selected from thegroup consisting of a naphthyl group, an anthryl group, a phenanthrylgroup, a naphthacenyl group, a pyrenyl group, a triphenylenyl group, anda chrysenyl group.
 18. The method of claim 12, wherein the heterocyclicacetylene portion comprises at least one selected from the groupconsisting of a pyridyl group, a pyridazinyl group, a pyrimidyl group, apyrazinyl group, a quinolyl group, an isoquinolyl group, a quinazolinylgroup, a cinnolinyl group, and a phthalazinyl group.
 19. The method ofclaim 12, wherein at least one of the diarylacetylene portion, thearylacetylene portion, and the heterocyclic acetylene portion has atleast one substituted group thereon.
 20. The method of claim 12, whereinthe copolymer comprises a diphenylacetylene portion and aphenylacetylene portion.
 21. The method of claim 12, wherein thecopolymer comprises from about 50% to about 99.9% by weight of thediarylacetylene portion and from about 50% to about 0.1% by weight of atleast one of the arylacetylene portion and the heterocyclic acetyleneportion.
 22. The method of claim 12, wherein the organic semiconductorlayer has a thickness of about 0.001 μm or more and about 5 μm or lessand the passive layer has a thickness of about 2 Å or more and about 0.1μm or less.
 23. A method of making an organic memory cell comprising:forming a first electrode comprising at least copper; forming a passivelayer comprising at least copper sulfide over the first electrode;forming an organic semiconductor layer over the passive layer, theorganic semiconductor layer comprising a copolymer, the copolymercomprising from about 0.05% to about 99.95% by weight ofdiphenylacetylene portion and from about 99.95% to about 0.05% by weightof phenylacetylene portion; and forming a second electrode over theorganic semiconductor layer.
 24. The method of claim 23, wherein theorganic semiconductor layer has a thickness of about 0.001 μm or moreand about 5 μm or less and the passive layer has a thickness of about 2Å or more and about 0.1 μm or less.